Mark Zuckerberg, the creator of social media giant Facebook and his wife, Priscilla Chan, were the most generous American donors in the country in 2013, with a gift of $992.2 million worth of Facebook stock to a Silicon Valley education foundation, according to The Chronicle of Philanthropy’s Philanthropy 50 list. The pair is the youngest ever to top the list.

The top 50 contributors on the list made a total of $7.7 billion in 2013, along with pledge of $2.9 billion, the biweekly newspaper reports.

Here’s a look at the top five, and how they donated their cash last year.

1Mark Zuckerberg and Priscilla Chan

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Facebook’s IPO may have seemed like a fumble earlier this year, but Zuckerberg and his wife were highly-generous with the networking giant’s stock.

The couple gave 18 million shares of stock, valued at $992.2 million, to the Silicon Valley Community Foundation in 2013. They donated the same amount of Facebook shares in 2012 to the fund, the Chronicle reports.

2George Mitchell

Cynthia and George Mitchell Foundation

Mitchell donated approximately $750 million to the Cynthia and George Mitchell Foundation last year. This foundation was established by George and his wife in 1978 and supports a variety of nonprofits throughout Texas, the Chronicle reports.

Mitchell, who was the founder of Mitchell Energy and Development, an oil and natural gas explore, passed away in July at 94 and left the donation to his charity.

3Philip and Penelope Knight

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The Nike co-founder chairman and his wife donated $500 million to the Oregon Health & Science University Foundation on the condition that university officials will raise an additional $500 million from other donors over the next two years.

The donations will endow a research project to detect deadly cancers as well fund recruitment of top faculty and research staff, scholarships to grad students, new equipment and more clinical trials, according to the Chronicle.

4Michael Bloomberg

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The former New York City Mayor and billionaire gave a total of $452 million to arts, education, environment and public health-nonprofits, as well as programs aimed to help city governments around the world to locate and test new ideas to make local government more efficient.

The Chronicle reports that Bloomberg has said he plans to spend more time focusing on his philanthropy efforts now that he is out of office after more than a decade serving as mayor of the Big Apple.

5John and Laura Arnold

Laura and John Arnold Foundation

This power couple gave $235.8 million to the Laura and John Arnold Foundation last year. John founded the hedge fund Centaurus Energy and Laura is a former corporate lawyer.

The foundation was created in 2008 and supports programs to improve the reliability of scientific research, K-12 public education, the criminal justice system and public-policy practices, according to the Chronicle’s report.